Technical Field of the Invention
The present invention relates to a special mortar mixture, which can be on the one hand employed as a finishing plaster on buildings, and in another variant as an insulating plaster that can be used for interior and exterior insulation of building structures. Further, this mortar mixture can be also used for protection from fire in the form of a lower or upper coat, but also to create a screed or floor finishes, such as in leveling mortar and repair mortar for horizontal applications. Finally, this mortar mixture can be also employed as casting mortar for a mold form, or in order to manufacture insulating plates for protection from fire or for general construction purposes. The invention also relates to a method for manufacturing this mortar mixture, as well as to its use, and finally to a construction wherein the exterior and interior walls are coated with it, or the screed floor is manufactured from it, or wherein the mortar mixture is built into fire protection insulation boards, or for other construction components manufactured from this mortar mixture.
An essential fact about this mortar mixture is that it is partially or fully made from very special lightweight materials instead of from traditional sands. It can be used in a building construction in which exterior or interior walls or the ceilings or the floor boards are newly manufactured in this manner or later restored.
Description of the Prior Art
Various lightweight materials are used today in new constructions as well as for refurbishing purposes, such as expanded clay, open-cell perlite, glass beads, Polystyrene (EPS) and other materials. These lightweight materials have various disadvantages:                Open-cell perlites have a deep compressive strength of <0.2 Nmm2 and they are highly water-absorbent.        Glass beads are very abrasive and their handling is therefore problematic, for example when they are used for mixing or pumping. In addition, the products are very expensive.        EPS (Polystyrene) is vapor-proof and it is not heat-resistant. In case of fire, EPS increases the heat due to its energy output. Moreover, EPS must be disposed of as hazardous waste.        
The development of efficient lightweight materials with a good insulation value and with a high fire-resistance value, which additionally also produce a please room climate because only very little water is absorbed, while the materials are permeable to water vapor and have a purely mineral character and thus are naturally also degradable, represents a major challenge. Lightweight construction materials are currently mixed on the EPS base with the plaster. However, EPS is not fire-resistant. Rockwool or specialty products made from expanded clay or from expanded mica are used as fire prevention measures. However, rockwool cannot withstand compressive load. Fire-resistant boards that are made from expanded clay or expanded mica are very expensive. The reference value for insulation is the heat transmittance and this value is expressed as the lambda value (A). The lower the value, the better is the resulting thermal insulation. Mortar or boards made from EPS have a λ value of 35 mW/mK, rockwool has a lambda value of 50-70 mW/Mk. For aerogel plasters are listed lambda values of 12-15 mW/mk. Such low lambda values for aerogel are, however, pure laboratory values. In practice, the lambda value in the mortar mixture will be increased after a mixing and pumping operation on the construction site because aerogel is mechanical stressed by the mixing and pumping operation. The same is true about mixing of mortar containing EPS beads or traditional open cell perlite, which withstands a compressive stress at 10% compression of <0.2 N/mm2. Mortar mixture from similar lightweight materials having a high pressure resistance also may not be used in floor areas in which a certain pressure resistance is always required. Other lightweight materials, such as glass are very expensive and in addition, they are exposed to a very high wear in the mixer, in the pump and in transport hoses and are therefore for this reason used only to a limited extend in the construction industry.
Old buildings and their refurbishment represent another specific issue. Although old buildings are often very pretty—and sometime these are genuine monuments—they usually contain a poorly insulating building envelope and they are generally difficult to insulate at a later point. The development of efficient insulating systems, such as a well insulating plaster or well insulating boards, is therefore a challenge also for this application. Due to fire safety reasons, insulation boards made from extruded polystyrene (EPS) or Styrofoam should be additionally also protected from the effect of heat.
In Switzerland, as an example, there are about 1.5 million old buildings. One has to live with this building stock because we often want to preserve these buildings. At the same time, however, the consumption of energy in the country increases. 4.5 million tons of light oil and 3 million cubic meters of natural gas are according to the Swiss Federal Office imported every year for energy, 43 percent of which are burned to heat buildings. In order to handle these energy resources in a more economical manner, there is no solution that would make it possible to avoid the issue of better insulation of these old houses. The same is true also about many other countries.
But how does one insulate an old, historical building—whether it is a timber house, a house from the art deco era, or an old burgher's house? Protection of cultural heritage does not allow for simply wrapping up historic facades in modern insulation.
In order to preserve the appearance of the wall of an old house, plaster works best. Even the lining of winding staircases, arches and retaining walls with traditional insulation boards may sometime be costly. Plaster boarding using insulating plaster can be very easily attached in narrow areas. Moreover, the plaster is located directly on the masonry and it does not have any gaps in which moisture can condense. In practice, a combination of insulation boards and insulating plasters is often employed. Large, flat surfaces are covered with insulation boards, while winding areas of the structure are provided with insulating plaster. Lightweight mortars are essentially suitable for the reprofiling or for leveling of horizontal surfaces in old as well as in new constructions. This makes is possible decrease the weight. These leveling mortars can be also used for self-leveling. It is important in this case that these mortars absorb only a small amount of water. Under these circumstances, the water requirement is low and, accordingly, the setting time is short, which speeds up the construction programs. Therefore, the room climate is optimal if the mortars which are applied to the floors or walls are permeable to vapor. Otherwise, there is the risk that mold could form in case of insufficient ventilation.
Aerogel is one of the best, if not the best, insulation material that can be produced on an industrial scale. The material, which is also known as “frozen smoke” due to its appearance, is made of about 5 percent of silicate—the remainder is air. Aerogel was used already in the sixties for insulation of space suits and it has as many as 15 entries in the Guinness Book of Records, including entries for “the best insulator” and “the lightest solid.” In construction, aerogel is already being used for instance as insulation material which can be blown into wall spacers, or used in the form of insulation boards made of nonwoven fabric. Aerogel beads are indeed extremely light, almost weightless, and they can be held between the thumb and forefinger. But as soon as you rub your fingers, they crumble. After two or three movements, only fine powder will remain. Good results can be achieved when the powder is gently stirred with water and the resulting plaster is applied manually. However, when the plaster is pumped at a pressure of 7 to 8 bars through the hose of a professional plaster machine, the mechanical stress destroys the aerogel and its insulating effect. This means that aerogel would have to be integrated in such a way in the plaster so that its effect is maintained even with machine pumping of the insulating plaster. Laboratory samples of materials developed by the Swiss Material Testing Institute EMPA in Dubendorf, Switzerland, resulted in a thermal conductivity of A=30 mW/mK. Therefore, aerogel insulating plaster should be more than twice as good as a conventional insulating plaster and it should have comparable or even better insulating properties than a board made of extruded polystyrene (EPS). Conventional insulating plasters have a lambda value between 65 and 90 mW/mk, the worst plasters have a lambda value of 110 or 130 mW/mK. For practical applications, aerogel insulating plaster is sprayed onto the masonry with a plaster machine and then smoothened. This soft insulating plaster must be then protected in another operation with a mortar containing embedded fabric. However, it has been shown that when aerogel is applied as a pumped plaster, significantly more heat passes through it, in particular when the pumping route to its application was long. Due to the mechanical stress on the aerogel in the pump, its effect is decreased and the lambda value is increased. With a pumping line that is 30 meters long, the heat transmission is increased and the lambda value is thus raised from 30 to 40 to 45 mW/mK.
Buildings are usually constructed for a lifetime of 50-70 years. The buildings are then often dismantled after this time period. Accordingly, it makes sense to build in a sustainable manner, which means that renewable or recyclable raw material should be used. The raw materials should be environmentally neutral and they should not have an EPS or polymer base, which must be disposed of in special landfills. This is because the high costs of the disposal results in high construction costs.
On the other hand, thermal insulation boards do not incur any damage as a result of their installation and there is no deterioration of their λ value. An aerogel has a λ value of 15 to 20 mW/mK, which means that it is a better value than that of an extruded polystyrene board (EPS board), which has a λ value of 33 mW/mK. Although not all insulation boards can be used, such boards are still ideal in situations in which a low λ value is required because they do offer a low λ value. Aerogel boards or aerogel insulating plasters are generally very expensive. If it were possible to use an insulating plaster with comparable λ values, this would be extremely interesting for many applications because the insulating plaster can be sprayed also onto angled locations of a structure with a simple spraying process.
With traditional lightweight materials, lightweight concrete or traditional plasters or mortars are already modified. These mortar mixtures, however, are often not suitable or they are expensive. Absorbent, strongly hygroscopic products tend to develop shrinkage cracks in the initial phase of the binding process. Lightweight construction materials made from EPS are not fire-resistant. They are the opposite of fire-resistant materials. These products supply additional energy (nourishment) for the fire and they thus speed up the spreading of the fire. Accordingly, additional fire prevention measures are in practice often required when EPS (Styrofoam) is used.
A completely different aspect relates to a finishing plaster. For finishing plasters are commonly used dispersion-based binders. A common formulation that has been used for such a dispersion-based finishing plaster up until now is as follows: approximately 90 volume percent consists of sands, preferably silica sands with different grains sizes, mixed to achieve an ideal screen size for dimensions from 0 to 5 mm. The sands have a density of approximately 1.9-2.2 kg/l. Approximately 10 volume percent is then represented by a water-based dispersion (glue). If necessary, an additive is also added, for example a foaming agent and/or other additives which can be added for homogenous drying or for temperature control. Such finishing plasters are usually supplied to carry out the plastering operation in 25 kg pressure vessels. These pressure vessels must be in a tall building moved several floors up, which is often done manually and thus correspondingly labor intensive. Depending on the type of the sand and whether it is more absorbent or less absorbent, a part of the dispersion will penetrate into the sand, which means that a large amount of the dispersion is required and that the system is therefore expensive. The sands absorb additional water and the finishing coat thus rapidly hardens. Accordingly, a large staff must be present at the construction site to make it possible to apply the finishing plaster homogeneously before it starts to harden. Otherwise, the transitions from one scaffolding to another scaffolding location are difficult to manage and this is then in many cases visible on the object.